This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7 119 from an application for Analog/Digital Display Adapter and a Computer System Having the Same earlier filed in the Korean Industrial Property Office on Apr. 29 1998 and there duly assigned Serial No. 15395/1998 and on Oct. 16 1998 and there duly assigned Serial No. 43766/1998.
1. Field of the Invention
The present invention relates to computer systems, and more particularly to a computer system having dual and triple display function that supports analog displays and digital displays.
2. Discussion of the Related Art
Conventionally, personal computers are equipped with cathode ray tube (CRT) monitors. Also, portable computers such as laptop and notebook computers chiefly use flat panel liquid crystal displays. Occasionally, a desktop computer is equipped with the liquid crystal display (LCD) monitor, although it is costly. Today, liquid crystal displays are considered as a substitute for the CRT display for their compactness and low power consumption.
In the meantime, display monitors adopting the LCD panel have been developed to be used with the desktop personal computer. The LCD monitor has advantages of low power consumption and low electromagnetic wave radiation. LCD monitors commonly include an interface circuitry that converts analog video signals inputted from the system host into digital video signals in order to drive every pixel of the LCD panel. In particular, advanced digital display systems use all-digital flat panel display interface that eliminates the analog-to-digital conversion of the video signals and transmits digital video data from a host video controller to the LCD monitor through high speed data channel. This solves the digital interface design problems such as increasing clock rates, data lines, and cable length. In this system, the video controller circuitry converts the video memory data into transferable form and reconstructs it once it gets to the display panel.
Yet there has not been provided in the desktop computer a display adapter or video card that supports that all-digital interface LCD monitor. Further, in the notebook computer, there has not been provided an external digital video output function that allows use of the all-digital interface LCD monitor.
Furthermore, there are cases where either the external monitor cable fails to connect with the external video port of the notebook computer or the external monitor is not supplied with the power. In either case, when the notebook computer system is set to output video signals through the external video port, the external monitor will not operate and thus nothing appeared on the monitor screen.
Japanese Patent 2-64693 discloses a computer in which a CRT and an LCD are both available from separate output ports on a computer. U.S. Pat. No. 5,608,418 for a Flat Panel Display Interface For a High Resolution Computer Graphics System to McNally discloses a graphics subsystem that contains a flat panel connector and a CRT connector. In addition, McNally shows that a color buffer circuit receives a flat panel sense data which indicates whether the flat panel display is coupled to the flat panel interface lines.
What is needed is a portable, notebook computer having an LCD display panel, that can accommodate hookups to another LCD digital flat panel display and a hookup to a CRT monitor. In this arrangement, the extra LCD display will contain circuitry that will let the notebook computer know whether the extra LCD display monitor is hooked up so that power will be delivered to the LCD hookup only when an LCD monitor is plugged into the LCD hookup.
The present invention is intended to solve the prior art problems, and it is therefore an object of the invention to provide a display adapter capable of supporting digital displays as well as analog displays.
It is another object of the invention to provide a computer display system having dual display adapters capable of connecting one of the displays depending upon the monitor cable connection state.
It is further object of the invention to provide a computer display system having dual display adapters capable of reducing power consumed in one display adapter depending upon the monitor cable connection state.
It is further yet another object to provide a triple display notebook computer where the notebook computer will support hookups with another LCD display and a CRT display.
It is still another object to provide a monitor for the LCD hookup lines so that power will only be delivered to the LCD hookup only if the extra LCD monitor is plugged into the LCD hookup.
In accordance with one aspect of the present invention, a desktop computer system is provided, which comprises: a main board having at least one expansion slot; and a display adapter installed in one of the expansion slot of the main board, in which the display adapter including: a video controller for providing analog video signals and digital video data with the CRT display and digital displays, respectively; a first video port for connecting with the CRT monitor cable; and a second video port for connecting with the digital display monitor.
In accordance with another aspect of the present invention, a display adapter for use in a computer system is provided, which comprises: a video controller for outputting serial analog video signals and parallel digital video signals; a first connector being coupled with the CRT monitor cable connector; a second connector being coupled with the digital monitor cable connector; and a digital transmitter for sending parallel digital video signals to a digital display through the second connector.
The display adapter further comprises a monitor cable sensing means for detecting connection of the digital monitor cable connector with the second connector, whereby a display enable signal is generated in the video controller and being sent to the digital transmitter when the connection between the digital monitor cable and the second connector has been completed.
Preferably, the digital monitor includes means for generating a signal to be sent to the second connector of the display adapter over the monitor cable, thereby informing the monitor cable connection with the second connector to the video controller.
Further, the display adapter further comprises a power supply control circuit for switching on/off of the supply voltages directed to the digital transmitter, in which the power supply control circuit responds to the signal fed from the digital monitor such that the supply voltages are supplied with the transmitter when the connection between the digital monitor cable and the second connector has been completed.
In accordance with the other aspect of the present invention, a portable computer system is provided, which comprises: a LCD panel hingedly attached to the main body of the portable computer; a main board having a display adapter; a video controller capable of providing digital video data with the LCD panel; a transmitter for sending parallel digital video data to an extra digital monitor; and an external video port for connecting a cable of the external digital monitor.
The display adapter according to this invention allows the video signal to be sent to one of the LCD monitor and CRT monitor, any one that is connected with the video card, regardless of the video start-up direction or video output path set in the computer system. Further, the display adapter of the invention is capable of reducing power consumed in the digital transmitter when the monitor cable is disconnected from the computer system.